1. Field of the invention
The present invention relates to a resistance element which constitutes a part of a hybrid IC, a chip resistor, etc., and includes a resistance film formed between a pair of electrodes on an insulating substrate, and a method for trimming such a resistance element.
2. Description of the prior art
FIG. 6 through FIG. 10 are illustrative views showing different examples of a conventional resistance element, respectively.
FIG. 6 shows a resistance element in which a resistance film 3 is formed between a pair of electrodes 1 and 2 on an insulating substrate (not shown) and a resistance value between the electrodes 1 and 2 is trimmed or adjusted by forming a linear trimming groove 4 in the resistance film 3. FIG. 7 shows a resistance element in which an L trimming groove 5 is formed in the resistance film 3 to trim or adjust the resistance value. In the resistance elements shown in FIG. 6 and in FIG. 7, a start point SP of the trimming groove is positioned at the outside of the resistance film 3, but an end point EP thereof exists within the resistance film 3. Therefore, a microcrack is susceptible to occur at a portion of the resistance film 3 in the vicinity of the end point EP. Therefore, when a large surge current flows between the electrodes 1 and 2, heat is locally generated by current concentration at the portion in the vicinity of the end point EP, which causes micro-crack which has been formed in trimming to become larger, and resultingly a, large change of the resistance value takes place.
In order to eliminate such a disadvantage, in Japanese Patent Application Laid-open No. 107806/1985 laid-open on June 13, 1985, a trimming method shown in FIG. 8 or FIG. 9 has been proposed. In FIG. 8, the start point SP and the end point EP are both positioned at the outside the resistance film 3 and a trimming groove 6 which is continued between the start point SP and the end point EP in a form of a circular arc is formed, whereby a resistance film portion 3a, which is independent of the resistance film 3 which extends between the electrodes 1 and 2, is formed. In addition, in FIG. 9, a trimming groove 7 is formed between the start point SP and the end point EP which are both positioned at the outside of the resistance film 3, which includes a first portion 7a which is extended from the start point SP in a direction orthogonally intersecting a line connecting the electrodes 1 and 2, a second point 7b which is started at an end of the first portion 7a and curved toward the same direction in a form of a circular arc and a third portion 7c which is started at an end of the second portion 7b and terminated at the end point EP and extended a direction opposite to the extending direction of the first portion 7a.
In the example shown in FIG. 8 or FIG. 9, a current flows between the electrodes 1 and 2 through a current path CP as shown by a dotted line. Therefore, in the example, since the current flows so as to intersect the trimming groove 6 or 7, at any portion of the trimming groove 6 or 7, change of the resistance value is large, and therefore, it is difficult to finely or precisely trim or adjust the resistance value
In addition, in Japanese Patent Application Laid-open No. 133504/1980 laid-open on Oct. 17, 1980, a resistance element as shown in FIG. 10 has been proposed. In an example as shown in FIG. 10, a trimming groove 8 is formed between the start point SP and the end point EP which are both positioned at the outside of the resistance film 3. The trimming groove 8 includes a first portion 8a which is started at the start point SP and extended in a direction orthogonally intersecting a line connecting the electrodes 1 and 2, a second portion 8b which is started at an end of the first portion 8a and extended in a direction parallel with the line connecting the electrodes 1 and 2, and a third portion 8c which is started at an end of the second portion 8b and extended toward the end point EP in a direction orthogonally intersecting the line connecting the electrodes 1 and 2. In this example, since a connecting portion between the first portion 8a and the second portion 8b and a connecting portion between the second portion 8b and the third portion 8c are both formed at a right angle, a micro-crack is susceptible to occur at that portion. Furthermore, in the example, as in to the examples shown in FIG. 8 and FIG. 9, there is a disadvantage that it is difficult to finely or precisely trim or adjust the resistance value.